Large area light sources employing light guides with edge lit end surfaces are known. These large area light sources all have in common the fact that they do not have a uniform thickness, which is desirable in many applications, such as back-lighting of liquid crystal displays (LCDs) for pagers, hand-held computers, organizers and the like. Examples of prior art light sources are described in the following patents:
U.S. Pat. No. 4,706,173 discloses a light reflecting apparatus which uses a lamp, probably a fluorescent lamp, with light impinging on a series of reflective surfaces which reflect the light into an opposite smooth surface.
U.S. Pat. No. 4,277,817 discloses two embodiments of a wedge-shaped body for directing light, preferably for back-lighting in LCDs.
U.S. Pat. No. 4,257,084 discloses a display which reflects light off an angled surface. The light is then transmitted through a diffused surface.
U.S. Pat. No. 4,323,951 discloses a display having generally laminar light transmissive layers, one of which has a roughened back surface whereby light will be transmitted through a front surface of the laminar unit.
U.S. Pat. No. 5,050,946 discloses a light pipe which has a planar front surface for back-lighting LCDs. Light is injected into the light pipe from the ends. The back surface has a series of planar portions parallel to the front surface connected by facets, which are angled so that the injected light reflects off the facets through the front surface. A reflector having a planar, highly reflective, highly scattering surface or a sawtoothed or grooved upper surface is located adjacent to and parallel with the light pipe back surface to reflect light escaping from the back surface back through the light pipe to exit the front surface.